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Author: search.filters.author.Singh, KirtiSubject: search.filters.subject.MAP kinase

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    Phosphorylation of AGO1a by MAP kinases is required for miRNA mediated resistance against Xanthomonas oryzae pv. oryzae infection in rice
    (Elsevier B.V., 2024) Singh, Kirti; Sharma, Deepika; Bhagat, Prakash Kumar; Tayyeba, Sumaira; Noryang, Stanzin; Sinha, Alok Krishna
    Bacterial leaf blight is a devastating disease caused by Xanthomonas oryzae pv. oryzae (Xoo) which causes severe crop loss in rice. The molecular mechanism that initiates defense against such pathogens remains unexplored. Reports have suggested crucial role of several miRNAs in regulating immune responses in plants. Argonaute (AGO) proteins have been implicated in imparting immunity against pathogens by using small RNAs as guide molecules. Here, we show that phosphorylation of rice AGO1a by MAP kinases is required for miRNA expression regulation during Xoo infection. AGO1a is induced in response to pathogen infection and is under the control of SA signaling pathway. The pathogen responsive MAP kinases MPK3, MPK4 and MPK6, interact with AGO1a in planta and can phosphorylate the protein in vitro. Overexpression of AGO1a extends disease resistance against Xoo in rice and leads to a higher accumulation of miRNAs. Conversely, overexpression of a non phosphorylatable mutant protein aggravates disease susceptibility and remarkably suppresses the miRNA expression levels. At a molecular level, phosphorylation of AGO1a by MAP kinase is required for increased accumulation of miRNAs during pathogen challenge. Taken together, the data suggests that OsAGO1a is a direct phosphorylation target of MAP kinases and this phosphorylation is crucial for its role in imparting disease resistance.
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    Phosphorylation of PIF3 by MPK6 is required for coordinated regulation of miRNA biogenesis and hypocotyl elongation in Arabidopsis
    (Elsevier B.V., 2023) Sharma, Deepika; Singh, Dhanraj; Singh, Kirti; Dwivedi, Aditi; Ranjan, Aashish; Sinha, Alok Krishna
    Light is one of the most important environmental factors that affect overall growth and development in plants. PHYTOCHROME INTERACTING FACTORs (PIFs) are negative regulators of photomorphogenesis. PIFs mediate light responses by interacting with downstream molecular partners and are essential regulators for hypocotyl elongation in Arabidopsis. Light induce activation of phytochromes (phys), promotes rapid phosphorylation, ubiquitination and degradation of PIFs. However the kinase responsible for the phosphorylation of PIFs and the signaling mechanism governing the adaptive changes leading to hypocotyl elongation to differential light intensities is not well understood. Here, we report interaction and phosphorylation of PIF3 by a mitogen-activated protein kinase 6 (MPK6) both in vitro and in vivo. Phosphorylation was significantly abolished when all the PIF3 putative phosphorylation sites were mutated to alanine. Further, we found that PIF3 directly binds to the bHLH binding domain in the promoter of RL responsive miRNA, miR163. Interestingly, phosphorylation status of PIF3 substantially affects the binding of PIF3 and mutated proteins to miR163 promoter. Further, overexpression of PIF3 affects the expression of red light (RL) responsive miRNAs and downstream genes involved in hypocotyl elongation and seedling development. These results suggest that MPK6-PIF3 module functions upstream of RL-responsive miRNAs and PIF3-regulated genes involved in photomorphogenesis, thus interconnecting these pathways together.